DESCRIPTION (APPLICANT'S ABSTRACT): HIV infections increasingly occur in persons with severe mental illness (SMI). Although descriptive studies have established high rates of HIV risk behavior among those with SMI, only a small body of research has shown that intensive cognitive-behavioral small group interventions can promote short-term change in HIV sexual risk practices. This application requests three years of support to evaluate the effectiveness of a community level intervention for people with SMI or those dually-diagnosed with SMI and substance abuse disorders (DD), who are formerly homeless, living in transitional housing programs (THPs). The intervention model integrates social cognitive theory (Bandura, 1986) and diffusion of innovation theory (Rogers, 1983). The community intervention will include three key components: 1) HIV risk reduction skills training group intervention appropriately tailored for SMI; 2) community norm change intervention mediated by popular opinion leaders living in THPs to created models, norms, and reinforcement supports for HIV risk reduction; and 3) THP staff training on HIV prevention approaches. Twelve THPs (320 residents across 6 demographically matched pairs) will be randomly assigned to the community-level intervention or the skills training group intervention only comparison condition. Assessments collected at baseline, post-group intervention, and 6- and 9-month follow-up points will be used to determine intervention outcome effects. It is hypothesized that, relative to participants in the group intervention-only THPS, participants in the community-level intervention THPs will exhibit at all follow-up points: a) lower levels of HIV sexual risk behavior; b) lower levels of alcohol and substance use behavior; and c) higher levels of HIV-related knowledge and normative perceptions, intentions, attitudes and beliefs concerning risk reduction and avoidance. If successful, this research will identify a community-level intervention for reducing and maintaining HIV risk reduction among formerly homeless persons with SMI or DD living in THPS. Since transitional housing is a common component of integrated systems of care for those with SMI or DD, the potential for broad dissemination of research findings throughout programs nationally is substantial.